Log4j RollingFileAppender configuration example

Log4j RollingFileAppender is an OutputStreamAppender that writes log messages to files, following a configured triggering policy about when a rollover (backup) should occur. It also has a configured rollover strategy about how to rollover the file.

Generally backup of log files are created based on file size, current date or both.

1. Log4j maven dependencies

<dependency>
    <groupId>log4j</groupId>
    <artifactId>log4j</artifactId>
    <version>1.2.17</version>
</dependency>

2. RollingFileAppender example – rollover based on log file size

This given configuration roll over th log files based on log file size. I have configured the log file size to be 10 MB. Change it as per your requirement.

2.1. log4j.properties

We can configure rolling file appender in log4j.properties in given way.

log4j.appender.rollingFile=org.apache.log4j.RollingFileAppender
log4j.appender.rollingFile.File=${LOG_DIR}/application.log
log4j.appender.rollingFile.layout=org.apache.log4j.PatternLayout
log4j.appender.rollingFile.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss} %-5p %m%n
log4j.appender.rollingFile.MaxFileSize=10MB
log4j.appender.rollingFile.MaxBackupIndex=5
log4j.appender.rollingFile.append=true

log4j.rootCategory=ALL, rollingFile

2.2. log4j.xml

<appender name="rollingFile" class="org.apache.log4j.RollingFileAppender">
    <param name="file" value="${LOG_DIR}/application.log" />
    <param name="MaxFileSize" value="10MB" />
    <param name="MaxBackupIndex" value="5" />
        <layout class="org.apache.log4j.PatternLayout">
            <param name="ConversionPattern" value="%d{yyyy-MM-dd HH:mm:ss} %-5p %m%n" />
        </layout>
</appender>

3. RollingFileAppender – rollover based on date time

We can roll over log files based on date time as well.

3.1. RollingFileAppender example

If using RollingFileAppender, then use TimeBasedRollingPolicy to specify when to roll over log files based on date time.

Notice the FileNamePattern property. It defines the name pattern for rolled over files. In given example, it will rename the rollover log files with date-month in log file name.

For example, pattern '{dd-MMM}' will rollover log file everyday of month. Similarly, '{MM-dd-yyyy-HH}' will rollover every hour.

We also use .gz extension so log4j will compress the log file automatically.

<appender name="rollingFile" class="org.apache.log4j.rolling.RollingFileAppender">
    <rollingPolicy class="org.apache.log4j.rolling.TimeBasedRollingPolicy">
        <param name="FileNamePattern" value="${LOG_DIR}/application.%d{dd-MMM}.log.gz" />
    </rollingPolicy>
    <layout class="org.apache.log4j.PatternLayout">
        <param name="ConversionPattern" value="%d{yyyy-MM-dd HH:mm:ss} %-5p - %m%n" />
    </layout>
</appender>

3.2. DailyRollingFileAppender example

To enable the daily rolling, log4j provides DailyRollingFileAppender which extends RollingFileAppender. Use it directly, if you want to roll over your log files daily.

<appender name="rollingFile" class="org.apache.log4j.rolling.DailyRollingFileAppender">
    <layout class="org.apache.log4j.PatternLayout">
        <param name="ConversionPattern" value="%d{yyyy-MM-dd HH:mm:ss} %-5p - %m%n" />
    </layout>
</appender>

4. RollingFileAppender – rollover based on both – log size and date time

If you want to rollover log files based on file size and date time both, then you need to use SizeBasedTriggeringPolicy and TimeBasedRollingPolicy both.

<appender name="rollingFile" class="org.apache.log4j.rolling.RollingFileAppender">
    <rollingPolicy 
    	class="org.apache.log4j.rolling.TimeBasedRollingPolicy">
        <param name="ActiveFileName" value="${LOG_DIR}/application.log" />
        <param name="FileNamePattern" value="${LOG_DIR}/application.%d{dd-MMM}.log.gz" />
    </rollingPolicy>
    <triggeringPolicy
        class="org.apache.log4j.rolling.SizeBasedTriggeringPolicy">
        <param name="MaxFileSize" value="10MB" />
    </triggeringPolicy>
    <layout class="org.apache.log4j.PatternLayout">
        <param name="ConversionPattern" value="%d{yyyy-MM-dd HH:mm:ss} %-5p - %m%n" />
    </layout>
</appender>

References:

Log4j Rolling File Appender Java Doc